There are a variety of cloth media filtration systems available for water and wastewater treatment. However, these systems have rotating frame assemblies supporting the cloth filter media and/or require separate effluent channels for effluent discharge.
For example, available disk filtration systems generally have a tank with an inlet and outlet and a rotatable filter frame assembly positioned between the inlet and outlet. Cloth filter media is stretched over disk type frame sections which are connected to a rotatable support structure, such as a center tube pipe. During filtration, influent flows into the tank and passes through the cloth filter media, through the hollow disk frame section and into the effluent center tube for discharge through the tank outlet. See, for example, U.S. Pat. No. 4,639,315. The cloth filter media is periodically cleaned by a variety of procedures, such as backwashing and/or high pressure spray while the disks are rotating. See, for example, U.S. Pat. Nos. 5,374,360, 5,876,612 and 6,090,298.
Similarly, another cloth media filtration system is generally referred to as drum filtration. In drum filtration systems, cloth filter media is stretched over support frames that form a large drum shape, as opposed to disks. The drums are attached to a center tube structure and together form a rotatable filter frame assembly. During filtration, influent flows into the tank and passes through the cloth filter media, depositing the suspended solids on the cloth. The filtered influent flows through the filter frame center tube and is discharged through the tank outlet. See, for example, U.S. Pat. No. 4,090,965. Like disk filtration, the cloth filter media is periodically cleaned while rotating by backwashing and the like.
A more recent development in cloth media filtration is stationary cloth media filtration systems invented by some of the same co-inventors as the present inventions and assigned to Aqua-Aerobic Systems, Inc. This development is shown and described in U.S. Pat. No. 6,858,140, which issued on Feb. 22, 2005, and is entitled “Process and Devices for Water and Wastewater Treatment Including Stationary Cloth Media Filtration. In general, this system includes one or more distinct sealed effluent plenums. A series of cloth filter media covered filter plates are attached to and in fluid communication with the effluent plenums. Influent flows into the filtration basin through influent plenums and passes through the hollow cloth filter media covered filter plates. The filtered influent is then discharged through the effluent plenums. The cloth filter media is periodically cleaned, typically by backwashing, using a traveling bridge type assembly and the like.
While the above described systems are effective for a variety of applications, there are some inherent limitations for other applications. For example, the rotating disk and drum cloth media filtration systems are limited in capacity because of the necessity for rotation of the assembly during filtration and cleaning, which limits the length of the assemblies. To increase their length and capacity, it is believed that intermediate supports, larger pumps and more backwash equipment would be required. In addition, such systems necessarily have at least one rotating seal that is a potential area for failure and contamination by infiltration of untreated influent. These systems also require motors and related equipment necessary to impart rotation to the assemblies.
The stationary cloth filter media discussed in U.S. Pat. No. 6,858,140 is also effective for certain types of applications. However, this system requires, among other things, separate effluent plenums and a series of cloth media filter plates attached to the effluent plenums. As such, a large number of seals (for example, between each filter plate where it is attached to the effluent plenums) are required, again, posing potential contamination problems.
In addition, in order to effectively and efficiently conduct the backwashing operation of stationary cloth filter media filtration systems, it is important that the backwash shoes maintain sufficient contact with the cloth filter media during the backwashing operation. This operation is complicated by the fact that in most typical installations, there are manufacturing and construction tolerances in the various components, materials and in their spatial relationship to one another. Thus, there is a need for improved traversing backwash systems to accommodate for such tolerances.